1. Field of the Invention
The present invention relates to a shake amount detection device, and an imaging device including the same.
2. Description of the Related Art
In recent years, imaging devices with camera shake correction functions have been gaining in popularity. With such an imaging device, a user can take a good image which is free from image blur due to a camera shake, without paying particular attention.
In general, a camera shake increases at a time of photographing with a long exposure time. In some cases, an image blur at a time of such long-exposure photography fails to be sufficiently corrected. In particular, when long-exposure photography in a macro-region is conducted, it is highly possible that an image blur cannot fully be corrected. The reason for this is that, in many cases, a translational shake cannot fully be corrected by conventional camera shake correction. Camera shakes can generally be classified into an angular shake and a translational shake. The angular shake is such a camera shake that the angle of the optical axis of the imaging device is varied. On the other hand, the translational shake is such a camera shake that the body of the imaging device is moved in a planar direction perpendicular to the optical axis. When the image magnification is small, the effect of image blur due to a translational shake is small. If the image magnification increases, the effect of image blur due to the translational shake becomes greater. Accordingly, in a macro-region in which the image magnification is large in general, the effect of image blur due to the translational shake increases, and sufficient image blur correction cannot be made. Consequently, the quality of images deteriorates.
Jpn. Pat. Appin. KOKAI Publication No. H7-225405 proposes a method of detecting a translational shake. An imaging device, which is proposed in this Jpn. Pat. Appin. KOKAI Publication No. H7-225405, includes an acceleration detection device configured to detect accelerations in directions of three axes acting on the imaging device; an angular velocity detection device configured to detect angular velocities about these three axes; attitude detection means for calculating a coordinate transformation matrix between a camera coordinate system and a coordinate system at rest, from the accelerations in the three-axis directions and the angular velocities about the three axis; and gravitational acceleration component calculation means for calculating, from the coordinate matrix, a gravitational acceleration velocity component in the camera coordinate system. The gravitational acceleration component is eliminated from the output of the acceleration detection device, and then a translational movement amount is calculated. Based on the calculated translational movement amount, image blur correction is made.
In addition, in the case of an imaging device including a movable component such as a shutter or an instant return mirror, vibration occurring due to the operation of the movable component may affect image blur correction. Japanese Patent No. 2897413 proposes a method in which, when vibration has occurred due to the operation of the movable component, the effect of the vibration in the calculation of shake information is reduced by prohibiting the calculation of shake information for a predetermined period until the output of an angular velocity sensor is stabilized.